1. doc.: IEEE 802.15-11-0877-00-004k Submission Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Discussions on SFD sequence length for LECIM FSK-PHY] Date Submitted: [Dec. 2011] Source: Mi-Kyung Oh, Sangsung Choi, Kwang-Roh Park (ETRI) Voice: +82 42 860 5680, FAX: +82 42 860 5218, E-Mail: ohmik@etri.re.kr Re: [802.15.TG4k] Abstract: This contribution is prepared to discuss about SFD sequence length for FSK PHY. Purpose: Notice:This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

2. doc.: IEEE 802.15-11-0877-00-004k Submission Outline The goal of this document is to discuss about SFD detection capability depending on the sequence length for LECIM FSK PHY. Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 2

3. doc.: IEEE 802.15-11-0877-00-004k Submission FSK Packet Format PHY packet format Reliability features in harsh LECIM environments –Preamble: multiple repetition of “01010101” –SFD: 2-octet is enough for reliable operation?? –PHR: FEC, Spreading –PSDU: FEC, Spreading, P-FSK Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 3 PHY Layer Preamble PHR FEC, Spreading, P-FSK PSDU SFD Multiple repetition of “01010101” FEC, Spreading ??

4. doc.: IEEE 802.15-11-0877-00-004k Submission SFD Detector One example: correlator-based SFD detector –Detection occurs when the correlator output exceeds the threshold Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 4 Detection threshold SFD detection threshold - If it is set to high value, the missing rate increases and false alarm rate decreases. - If it is set to small value, the false alarm rate increases and missing rate decreases. SFD sync. position

5. doc.: IEEE 802.15-11-0877-00-004k Submission Simulations on SFD Detector Simulation environments –Packet format: Preamble: 8-octet (8 multiples of “01010101”) SFD: 2-octet, 3-octet, 4-octet, 5-octet, 6-octet Data: 127-octet random data –Modulation: 2-level FSK –Demodulation: non-coherent & hard decision for simplicity –SFD detector: correlator-based detector Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 5

6. doc.: IEEE 802.15-11-0877-00-004k Submission Simulations on SFD Detector False alarm rate –In this simulation, we consider only the case when the SFD correlator output has its maximum during preamble. –Comment: If the detection threshold is used, the false alarm rate becomes dependent on missing rate. Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 6 SFD correlator output at SNR=3dB Preamble duration Real SFD sync. positionMax. value occurs in preamble duration => False alarm

7. doc.: IEEE 802.15-11-0877-00-004k Submission Simulations on SFD detector Simulation results: False alarm rate –Longer SFD sequence gives better performance Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 7 Performance difference is relatively small

8. doc.: IEEE 802.15-11-0877-00-004k Submission Discussions (1) Good channel environments with high EIRP –Operating SNR would be high Non-coherent FSK receiver requires 11dB @ BER 10 -5 –PHR & PSDU recovery The FSK basic feature is enough No need for FEC, spreading or P-FSK –SFD detection False alarm rate is negligible at high operating SNR SFD sequence : 2-octet would be enough Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 8

9. doc.: IEEE 802.15-11-0877-00-004k Submission Discussions (2) Harsh channel environments with low EIRP –Operating SNR would be low: e.g., SNR ≤ 4dB –PHR & PSDU recovery The FSK selection features should be used –FEC, spreading, P-FSK Once SFD detection is successful, PHR & PSDU have capabilities of restoring information bits at low SNR. –SFD detection False alarm rate becomes one of main factors for packet recovery at low operating SNR 2-octet SFD sequence: false alarm rate is relatively high at low SNR Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 9

10. doc.: IEEE 802.15-11-0877-00-004k Submission Discussions (3) The SFD part is required to have similar capability compared with PHR & PSDU parts in harsh environments –It can be possible by lengthening the SFD sequence. Repetition of 4g SFD sequence with length 16 as in the doc. 774-01 –It will be good for 15.4g interoperability. –SFD detector can use full SFD sequence or part of SFD sequence according to its capability and channel condition –How many repetitions? 2 repetitions (4-octet SFD) would be suitable since 5- octet SFD and 6-octet SFD do not give the dramatic performance enhancement. Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 10

11. doc.: IEEE 802.15-11-0877-00-004k Submission Discussions (4) Still, 4-octet SFD is not enough at low SNR and the false alarm rate is relatively high. Once SFD detection with false alarm occurs, the receiver starts to recover PHR & PSDU bits. –It entails unnecessary energy consumption. –Validity check for PHR can stop this unnecessary PSDU recovery. Simple validity check method for PHR –Parity check –How many parity bits? Need more discussions Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 11

12. doc.: IEEE 802.15-11-0877-00-004k Submission Conclusions SFD sequence –Simulation results show that 4-octet SFD is suitable –SFD Pattern: 2 repetitions of 4g SFD sequence –However, long SFD sequence may not be required at high SNR  can we select 2-octet SFD and 4-octet SFD according to channel condition? Validity check for PHR –Simple parity check can stop PSDU recovery to conserve energy even if SFD detection with false alarm occurs Dec. 2011 Mi-Kyung Oh, Sangsung Choi (ETRI)Slide 12